In this proposal we intend to identify the regions of the plasminogen isozymes which contain carbohydrate and show how the isozymes differ in this regard. We also intend to define a role for the carbohydrate in determining the structural and activation differences of the plasminogen isozymes. We also intend to learn more concerning the mechanism of activation of plasminogen. During this year, we will examine the fragmentation pattern of streptokinase during plasminogen activation and identify and examine proactivators which exist in the plasma of streptokinase-insensitive species of animals. These proactivators, which are not plasminogen or plasmin, interact with streptokinase to form a molecule which converts plasminogen to plasmin. BIBLIOGRAPHIC REFERENCES: Barlow, G. Finley, R. and Castellino, F.J. (1976) Immunological Comparison of Native Streptokinase with Streptokinase Fragments, Thromb. Res. 8, 237-242. Sodetz, J.M., Violand, B.N. and Castellino, F.J. (1976) A Kinetic Comparison of the Rabbit Plasmin Isozymes, Arch. Biochem. Biophys. 174, 209-215.